Outboard marine propulsion devices and exhaust systems for outboard marine propulsion devices

ABSTRACT

An outboard marine propulsion device comprises an internal combustion engine having a cylinder head and a cylinder block; and an exhaust manifold that discharges exhaust gases from the engine towards a vertically extending catalyst housing. The exhaust manifold has a plurality of horizontally extending inlet runners upwardly that receive the exhaust gases from the engine, and a vertically extending collecting passage that conveys the exhaust gases from the plurality of horizontally extending inlet runners to a bend that redirects the exhaust gases downwardly towards the catalyst housing.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/906,025, filed Nov. 19, 2013, which is hereby incorporated by reference in entirety.

FIELD

The present disclosure relates to marine engines and cooling systems for marine engines, and particularly to in-line, four-stroke marine engines having one or more catalysts for treating exhaust gas.

BACKGROUND

The following U.S. Patents are incorporated herein by reference:

U.S. Pat. No. 8,783,217 discloses a cooling system for a marine engine with various cooling channels and passages. The cooling system allows the rates of flow of its internal streams of water to be preselected so that heat can be advantageously removed at varying rates for different portions of the engine. In addition, the direction of flow of cooling water through the various passages assists in the removal of heat from different portions of the engine at different rates so that overheating can be avoided in certain areas, such as the exhaust manifold and cylinder head, while overcooling is avoided in other areas, such as the engine block.

U.S. Pat. No. 8,763,566 discloses a cooling system for a marine engine with various cooling channels, which allow the advantageous removal of heat at different rates from different portions of the engine. A split flow of water is conducted through the cylinder head, in opposite directions, to individually cool the exhaust port and intake ports at different rates. This increases the velocity of coolant flow in the downward direction through the cylinder head to avoid the accumulation of air bubbles and the formation of air pockets that could otherwise cause hot spots within the cylinder head. A parallel coolant path is provided so that a certain quantity of water can bypass the engine block and avoid overcooling the cylinder walls.

U.S. Pat. No. 8,696,394 discloses a marine propulsion system comprising an internal combustion engine, a cooling circuit carrying cooling fluid that cools the internal combustion engine, a sump holding oil that drains from the internal combustion engine, and a heat exchanger receiving the cooling fluid. The oil that drains from the internal combustion engine to the sump passes through and is cooled by the heat exchanger.

U.S. Pat. No. 8,668,538 discloses a marine engine having an exhaust system comprising a cylinder block comprising first and second banks of cylinders that are disposed along a longitudinal axis and that extend transversely with respect to each other in a V-shape so as to define a valley there between. A catalyst receptacle is disposed in the valley and contains at least one catalyst that treats exhaust gas from the marine engine. An exhaust manifold conveys exhaust gas from the marine engine to the catalyst receptacle. The exhaust manifold has a first port receiving exhaust gas from the first bank of cylinders, a second port receiving exhaust gas from the second bank of cylinders, and a conduit conveying the exhaust gas from the first and second ports to the catalyst receptacle, wherein from the first and second ports to the catalyst receptacle, the conduit only reverses direction once with respect to the longitudinal axis.

U.S. Pat. No. 8,479,691 discloses a cooling system for a marine engine with various cooling channels which allow the advantageous removal of heat at different rates from different portions of the engine. A split flow of water is conducted through the cylinder head, in opposite directions, to individually cool the exhaust port and intake ports at different rates. This increases the velocity of coolant flow in the downward direction through the cylinder head to avoid the accumulation of air bubbles and the formation of air pockets that could otherwise cause hot spots within the cylinder head. A parallel coolant path is provided so that a certain quantity of water can bypass the engine block and avoid overcooling the cylinder walls.

U.S. Pat. No. 8,540,536 discloses a cooling system for a marine engine having an elongated exhaust conduit comprising a first end receiving hot exhaust gas from the marine engine and a second end discharging the exhaust gas. An elongated cooling water jacket extends adjacent to the exhaust conduit. The cooling water jacket receives raw cooling water at a location proximate to the second end of the exhaust conduit, conveys raw cooling water adjacent to the exhaust conduit to thereby cool the exhaust conduit and warm the raw cooling water, and thereafter discharges the warmed cooling water to cool the internal combustion engine.

U.S. Pat. No. 8,500,501 discloses an outboard marine drive including a cooling system that draws cooling water from a body of water in which the outboard marine drive is operating, and supplies the cooling water through cooling passages in an exhaust tube in the driveshaft housing, a catalyst housing, and an exhaust manifold, and thereafter through cooling passages in the cylinder head and the cylinder block of the engine. A 3-pass exhaust manifold is provided. A method is provided for preventing condensate formation in a cylinder head, catalyst housing, and exhaust manifold of an internal combustion engine of a powerhead in an outboard marine drive.

U.S. Pat. No. 8,402,930 discloses a cooling system for a marine engine with various cooling channels and passages which allow the rates of flow of its internal streams of water to be preselected so that heat can be advantageously removed at varying rates for different portions of the engine. In addition, the direction of flow of cooling water through the various passages assists in the removal of heat from different portions of the engine at different rates so that overheating can be avoided in certain areas, such as the exhaust manifold and cylinder head, while overcooling is avoided in other areas, such as the engine block.

U.S. Pat. No. 8,388,393 discloses an outboard motor that includes an internal combustion engine, a driveshaft housing, a molded adapter plate connecting the internal combustion engine and the driveshaft housing; and an elongated exhaust conduit conveying hot exhaust gas from the internal combustion engine, the exhaust conduit extending from a first end portion located proximate to the internal combustion engine to a second end portion located proximate to the driveshaft housing. The exhaust conduit and adapter plate are separate components.

U.S. Pat. No. 8,038,493 discloses a catalyzed exhaust system for an outboard motor engine that rotates its catalyst device in a catalyst housing above an adapter plate, which supports the engine and separates it from the driveshaft housing. The exhaust gas is directed initially in an upwardly direction and then is turned downwardly to provide space for location and easy access to the catalyst device. A coolant, such as water drawn from a body of water, is reversed in direction of flow several times in order to advantageously fill certain cooling channels in an upward direction. In addition, various coolant channels are vented to remove potential pockets of air in their upper regions.

U.S. Pat. No. 7,954,314 discloses an engine provided with a cavity so that a catalyst member can be contained within the engine when an engine head portion is attached to an engine block portion. This attachment of the engine head portion and engine block portion, which forms the engine structure, captivates the catalyst member within the cavity without the need for additional brackets and housing structures. The cavity is preferably located above or at the upper regions of first and second exhaust conduits which direct exhaust upwardly from the engine head portion toward the cavity and downwardly from the cavity within the engine block portion. The first and second exhaust conduits are preferably formed as integral structures within the engine head portion and engine block portion.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

In certain examples, an outboard marine propulsion device comprises an internal combustion engine having a cylinder head and a cylinder block; and an exhaust manifold that discharges exhaust gases from the engine toward a vertically extending catalyst housing. The exhaust manifold has a plurality of horizontally extending inlet runners that receive the exhaust gases from the engine, and a vertically extending collecting passage that conveys the exhaust gases from the plurality of horizontally extending inlet runners upwardly to a bend that redirects the exhaust gases downwardly towards the catalyst housing. The bend can comprise a curved radially outer wall. An uppermost inlet runner in the plurality of horizontally extending inlet runners can have an uppermost radially inner wall that horizontally extends to an uppermost location on the curved radially outer wall so that the exhaust gases flow horizontally through the collecting passage and then downwardly in the bend.

In certain examples, a catalyst is disposed in the catalyst housing. The catalyst vertically extends along a catalyst centerline. The bend comprises an outlet end that extends along an outlet centerline that is horizontally offset from the catalyst centerline. An exhaust gas concentration sensor can be located upstream of the catalyst and downstream of the bend. A flange can be formed on the upstream end of the catalyst, wherein the flange is sandwiched between the exhaust manifold and the catalyst housing to retain the catalyst in place.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples are described with reference to the following drawing figures. The same numbers are used throughout the figures to reference like features and components.

FIG. 1 is a perspective view of an outboard marine propulsion device having an engine, and upper cowl, an adapter plate, a driveshaft housing and a gearcase.

FIG. 2 is an exploded view of an outboard marine propulsion device having an exhaust system, which is shown separated from the engine.

FIGS. 3 and 4 are exploded perspective views of an upper portion of the exhaust system of the outboard marine propulsion device.

FIG. 5 is an exploded perspective view of the exhaust system.

FIG. 6 is an exploded view of a lower portion of the outboard marine propulsion device.

FIGS. 7 and 8 are different cross-sectional views of an upper portion of the outboard marine propulsion device.

FIG. 9 is a cross-sectional view of an upper portion of the outboard marine propulsion device, wherein the section is taken along a vertical plane.

FIG. 10 is a cross-sectional view of the outboard marine propulsion device, the section taken along a vertical plane.

FIG. 11 is a cross-sectional view of a lower portion of the outboard marine propulsion device, showing the gearcase and the driveshaft housing, the section taken along a vertical plane.

FIG. 12 is a cross-sectional view of the outboard marine propulsion device, wherein the section is taken along multiple vertical planes.

FIGS. 13 and 14 are cross-sectional top views of the outboard marine propulsion device, wherein the sections are taken along horizontal planes at different heights.

FIG. 15 is a front view of the outboard marine propulsion device.

FIG. 16 is a front view of the outboard marine propulsion device.

FIG. 17 is a rear view of the outboard marine propulsion device.

FIG. 18 is also a rear view of the outboard marine propulsion device with several peripheral components and assemblies removed.

FIG. 19 is a rear view of an upper portion of the outboard marine propulsion device with several peripheral components and assemblies removed.

FIG. 20 is a top view of the gasket disposed between the exhaust manifold and the catalyst housing.

FIGS. 21 and 22 are schematics of example cooling systems for the outboard marine propulsion device, wherein the cooling water makes three passes through the exhaust manifold.

FIGS. 23-26 show a water core (the cooling passages) of the outboard marine propulsion device exhaust system described and shown above.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1-6 depict an outboard marine propulsion device 10 comprising, an internal combustion engine 12, an adapter plate 14, a driveshaft housing 16, and a gearcase 18. The configuration of the engine 12 can vary. In the example of FIG. 1, the engine 10 is a four-stroke engine comprising a cylinder block 20 with a plurality of cylinders (e.g., four cylinders) 22 (FIG. 7), which are aligned in a substantially vertical direction V, and a cylinder head 24. Exhaust gases from the engine 12 are routed from the cylinder head 24 to a catalyst housing 26 by an exhaust manifold 28. The catalyst housing 26 contains at least one catalyst 30 that treats the exhaust gases. After passing through the catalyst housing 26, the exhaust gases flow into a lower exhaust pipe 32, which extends into the driveshaft housing 16. The outboard marine propulsion device 10 is mounted to a marine vessel by a transom mount assembly 19.

FIG. 2 shows the exhaust system 34 separated from the engine 12. As shown, the exhaust system 34, including the exhaust manifold 28, catalyst housing 26 and lower exhaust pipe 32 may be removed from the engine 12. The exhaust system 34 comprises the exhaust manifold 28, the catalyst housing 26 and the lower exhaust pipe 32.

FIGS. 3 and 4 are exploded perspective views of an upper portion of the exhaust system 34. As noted above, the upper portion (i.e. the portion above the adapter plate) includes the exhaust manifold 28 and the catalyst housing 26, which includes at least one catalyst 30. The upper portion also includes a first gas concentration sensor 36 disposed upstream of the catalyst 30 (i.e. a pre-catalyst oxygen sensor) and second gas concentration sensor 37 disposed downstream of the catalyst 30 (i.e. a post-catalyst oxygen sensor). A voltage regulator 38 is attached to the outside of the exhaust manifold 28, in a position that puts it in thermal communication with cooling passages (to be explained further herein below) for cooling the exhaust manifold 28, thereby allowing the voltage regulator 38 to be cooled by cooling water flowing through the cooling passages. As shown in FIG. 4, a gasket 42 may be positioned between the connecting surfaces 44, 46 of the exhaust manifold 28 and the catalyst housing 26 to provide a seal therebetween. The gasket 42 is shown in greater detail in FIG. 20 and is also discussed in greater detail in connection with FIG. 20.

FIG. 5 is an exploded perspective view of the exhaust system 34, including the exhaust manifold 28, the catalyst 30, the catalyst housing 26, and the lower exhaust pipe 32.

FIG. 6 is an exploded view of a lower portion of the outboard marine propulsion device 10, including the adapter plate 14, an isolator/seal 48, the lower exhaust pipe 32, the driveshaft housing 16, an oil sump 17 in the driveshaft housing 16, and the gearcase 18. The isolator/seal 48 is provided between the adapter plate 14 and the lower exhaust pipe 32. During assembly, the lower exhaust pipe 32 is inserted into the driveshaft housing 16.

FIGS. 7 and 8 are different cross sectional views of an upper portion of the outboard marine propulsion device 10, the sections being taken along different vertical planes, showing the cylinder block 20, the exhaust manifold 28, the gasket 42, the catalyst housing 26, the catalyst 30 and the adapter plate 14. Included in the exhaust manifold 28 is an exhaust passage 50 through which the exhaust gases flow. As shown in FIGS. 7 and 8, a cooling water jacket 52 is disposed on the exhaust manifold 28 and a cooling water jacket 54 is disposed on the catalyst housing 26, substantially surrounding the exhaust passage 50 and the catalyst 30. The cooling water jackets 52, 54 direct cooling water around and in thermal communication with the exhaust passage 50 and the catalyst housing 26 to cool the exhaust gases and the catalyst 30.

FIG. 9 is a cross sectional view of an upper portion of the engine 12, the section being taken along a vertical plane. In FIG. 9, the path of exhaust gas flow through the engine 12 is shown with solid arrows, while the path of cooling water flow is shown with dashed arrows. Exhaust gases flow from piston/cylinders in the cylinder head 24, which correspond to the plurality of cylinders 22 into exhaust manifold inlet runners 58 on the exhaust manifold 28, where the exhaust gases are guided by the exhaust passage 50. Cooling water flows through the cooling water jackets 52, 54 around the exhaust manifold inlet runners 58, working in a generally upward direction, from the lowermost exhaust manifold inlet runners 58 to the upper most exhaust manifold inlet runners 58. A joint 60 between the cooling water jacket 52 and a cooling passage 62 in the cylinder head 24 is at substantially the highest point in the cooling water system, so that any air trapped in the system will go through this joint.

FIG. 10 is another cross sectional view of the engine 12, the section being taken along a vertical plane. The path of exhaust gas flow through the engine 12 is again shown with solid arrows, while the path of coolant water flow is shown with dashed arrows. As shown, exhaust gases flow from the exhaust manifold inlet runners 58 into a collecting passage 64, where it is then guided through a bend 66, into a generally downward direction of flow, toward the catalyst 30. The collecting passage 64 is substantially vertically oriented, and the catalyst housing 26 is substantially parallel thereto, such that exhaust gases from the lower most exhaust manifold inlet runners 58 flow generally upward in the collecting passage 64, makes a 180 degree turn in the bend 66, and then flows generally downward through the catalyst housing 26 (and catalyst 30), into the lower exhaust pipe 32. A centerline C1 of the catalyst 30 (and catalyst housing 26) is offset from a centerline C2 of the exhaust passage 50 in order to promote even distribution of exhaust gasses across catalyst 30. Exhaust gas flow tends to “hug” the outside surface of the exhaust passage 50, such that if the catalyst 30 were in line with the exhaust passage 50 (rather than offset), a majority of the exhaust gases would pass through only an outside portion of the catalyst 30, resulting in uneven degradation (wear) of the catalyst 30. This offset helps to ensure that the catalyst 30 is used more evenly (for utilization efficiency) and degrades (wears) more evenly, thereby prolonging its life.

As shown in FIG. 10, the cooling water flows up from the driveshaft housing 16 through a cooling water jacket 68 disposed on the lower exhaust pipe 32. From the cooling water jacket 68, cooling water continues to flow in a generally upward direction through the cooling water jacket 54 on the catalyst housing 26 and to the cooling water jacket 52 on the exhaust manifold 28. In the cooling water jacket 52 on the exhaust manifold 28, the cooling water flows through passages surrounding the collecting passage 64, bend 66, and the exhaust manifold inlet runners 58. In this manner, substantially all portions of the exhaust system 34 (e.g., the exhaust manifold 28, the catalyst housing 26, and the lower exhaust pipe 32) are effectively cooled.

As shown in FIG. 10, there is a first small opening 70 in the top of the cooling water jacket 52 on the exhaust manifold 28 at the bend 66 and a second small opening 72 in the top of the cooling water jacket 52 at the exhaust manifold inlet runners 58 to allow air to bleed out of the system. It can be desirable to include a “jumper” 73 connecting these two openings and allowing any air trapped in the respective cooling passages to bleed out. In the alternative, an orifice at the highest point of the cooling water jacket 52 on the exhaust manifold 28, connecting the noted cooling passages may perform the same function.

Further, it may be desirable to include a drain hole 74 at the lowest point of the cooling water jacket 52 on the exhaust manifold 28 to allow any cooling water to drain out of the cooling water jacket 52 when the engine 12 is not in use. If water is trapped in the system and freezes in cold weather, it can cause significant and costly engine problems. The drain hole 74 may allow water to drain back to the cylinder head 24, to somewhere else on the engine 12, or may be connected to a hose that directs the water outside the engine 12. As shown, the cooling water makes three passes along the exhaust manifold 28 helping to promote maximum cooling of the exhaust gases passing therethrough.

FIG. 11 is a cross sectional view of the lower portion of the outboard marine propulsion device 10 showing the gearcase 18 and the driveshaft housing 16, wherein the section is taken along a vertical plane. As in previous Figures, the flow of exhaust gases is shown with solid arrows, while the flow of cooling water is shown with dashed arrows. As shown, exhaust gases generally flow in a downward direction through the lower exhaust pipe 32 and into the gearcase 18. The gearcase 18 includes a sprayer 76 that injects water into the exhaust gases flowing out of the bottom of the lower exhaust pipe 32, further cooling the exhaust gases before exiting the outboard marine propulsion device 10. The lower exhaust pipe 32 includes an idle relief passage 78 that allows for communication between the cooling water jacket 68 on the lower exhaust pipe 32 and the lower exhaust passage 50. Depending on the mode of operation of the engine 12, cooling water may flow into the lower exhaust passage 50 or exhaust gases may flow out of the lower exhaust passage 50 (or a combination thereof).

FIG. 12 is a cross sectional view of the engine 12, where the section is taken along multiple vertical planes so that a substantial portion of the exhaust system can be seen. FIGS. 13 and 14 are cross sectional top views of the engine 12, with sections being taken along horizontal planes at different heights. The section plane of FIG. 13 is at a height that cuts through the catalyst housing 26, catalyst 30, and cylinders 22 whereas the section plane of FIG. 14 is higher, so the top of the catalyst housing 26 is visible and the exhaust passage of the topmost cylinder 22 is sectioned.

FIG. 15 is a front view of the outboard marine propulsion device 10. FIG. 16 is also a front view of the outboard marine propulsion device 10 with several peripheral components and assemblies removed. FIG. 17 is a rear view of the outboard marine propulsion device 10. FIG. 18 is also a rear view of the outboard marine propulsion device 10 with several peripheral components and assemblies removed. FIG. 19 is a rear view of an upper portion of the outboard marine propulsion device 10 with several peripheral components and assemblies removed.

FIG. 20 is a top view of the gasket 42 disposed between the exhaust manifold 28 and the catalyst housing 26. A plurality of bolt holes 41 are spaced around the gasket 42 for receiving bolts that secure the gasket 42 in place. In addition to providing a seal between the exhaust manifold 28 and the catalyst housing 26, the gasket 42 can operate as a spring that applies force to the catalyst 30, thereby helping to secure the catalyst 30 in place. The gasket 42 also has several, differently sized holes 82 that are sized and spaced to direct flow of cooling water from the cooling water jacket 54 on the catalyst housing 26 to the cooling water jacket 52 on the exhaust manifold 28. The restriction provided by the gasket 42 forces cooling water toward regions of the cooling passages that may otherwise not get sufficient flow of cooling water. Further discussion of this figure is provided herein below.

FIGS. 21 and 22 show schematics of exemplary cooling systems for the outboard marine propulsion device 10, wherein the cooling water makes three passes through the cooling water jacket 52 on the exhaust manifold 28. Further discussion of these figures is provided herein below.

FIGS. 23-26 show the water core (the cooling passages) of the outboard marine propulsion device 10 described and shown above. The cooling water jacket 68 on the lower exhaust pipe 32 picks up water in the gearcase 18 (taken from the body of water outside the outboard marine propulsion device 10), directs it upward to the cooling water jacket 54 on the catalyst housing 26, and then into the cooling water jacket 52 on the exhaust manifold 28. As shown well in FIGS. 25 and 26, there is a gap or disconnect 84 between the cooling jacket passages that cool the collecting passage 64 and the cooling jacket passages that cool the exhaust manifold inlet runners 58. As discussed briefly above, a first small opening 70 may exist in the cooling water jacket 52 at the top of the exhaust manifold 28 (at the top of the bend 66) and a second small opening 72 may exist in the cooling water jacket 52 at the top of the exhaust manifold inlet runners 58. The first and second small openings 70, 72 may be surrounded by a first small boss (around 86) on the top of the bend 66 and a second small boss (around 88) on the top of the exhaust manifold inlet runners 58. These two small bosses (and the openings 70, 72) may be connected together with a passage or hose to provide an air bleed between the two separated cooling passages, thereby preventing air pockets from being trapped in the cooling passages.

Referring to FIGS. 1-10 and 20, it will thus be seen that the present disclosure provides an outboard marine propulsion device 10 having an internal combustion engine 12 that includes a cylinder head 24 and a cylinder block 20. An exhaust manifold 28 discharges exhaust gases from the engine 12 to a vertically elongated exhaust pipe 32. The exhaust manifold 28 has a plurality of exhaust manifold inlet runners 58 that receive the exhaust gases from the engine 12 and a collecting passage 64 that conveys the exhaust gases upwardly from the plurality of exhaust manifold inlet runners 58 to a bend 66 that redirects the exhaust gases downwardly towards the exhaust pipe 32. A cooling water jacket 52 is provided on the exhaust manifold 28. The cooling water jacket 52 conveys cooling water alongside the exhaust manifold 28.

Referring to FIGS. 21 and 22, a series of cooling passages 62, 63 are formed in the cylinder head 24. The cooling passages 62, 63 convey the cooling water from the cooling water jacket 52 on the exhaust manifold 28 to a series of cooling passages 90, 92 in the cylinder block 20. A catalyst housing 26 is coupled to the exhaust manifold 28 and a cooling water jacket 54 is disposed on the catalyst housing 26. The cooling water jacket 54 carries cooling water alongside the catalyst housing 26. A flow disrupter disrupts flow of cooling water past the catalyst housing 26 to the cooling water jacket 52 on the exhaust manifold 28. In this example, the flow disrupter is formed by the gasket 42 that is disposed between the cooling water jacket 54 on the catalyst housing 26 and the cooling water jacket 52 on the exhaust manifold 28. The gasket 42 has a peripheral surface 94 and has a non-symmetric series of holes 82 (see FIG. 20) that are formed around the peripheral surface 94. The holes 82 are shaped and spaced apart along the peripheral surface 94 to direct flow of cooling water to non-jacketed areas, e.g. 96 (see FIG. 4) of the exhaust manifold 28. The holes 82 can further be shaped and spaced apart to control flow of cooling water towards the one or more gas concentration sensors 36, 37 that sense oxygen content of the exhaust gases flowing through the exhaust system 34. In this example, the sensors 36, 37 extend through bosses 98, 100 (see FIG. 8) which create potential hot spots in the exhaust system 34, which otherwise would create problems if not for the redirection of cooling water via the noted flow disrupter.

Referring to FIGS. 21 and 22, a pump 102 pumps cooling water from upstream to downstream through the cooling water jacket 68 on the lower exhaust pipe 32, the cooling water jacket 54 on the catalyst housing 26, the cooling water jacket 52 on the exhaust manifold 28, the series of cooling passages 62, 63 in the cylinder head 24, and the series of cooling passages 90, 92 in the cylinder block 20, etc. A tell-tale outlet 104 is configured to receive cooling water at a location that is upstream of the cooling water jacket on the catalyst housing 26. The tell-tale outlet 104 receives the cooling water through a strainer 69 and then discharges it from the outboard marine propulsion device 10. A portion of the cooling water is also discharged to the flow of exhaust gases via the noted sprayer 76 (see FIG. 11). The location of the tell-tale outlet 104 upstream of the catalyst 30 can vary. In this example, the tell-tale outlet 104 is connected to and receives the cooling water from the cooling water jacket 68 on the exhaust pipe 32. Cooling water located downstream of the catalyst housing 26 is discharged from the outboard marine propulsion device 10 only through an actively controlled outlet 106. More specifically a thermostat 108 actively controls flow of cooling water to the outlet 106. The thermostat 108 is located downstream of the cooling passages 62, 63 in the cylinder head 24 and is configured to reduce flow of cooling water through the engine 12 at idle engine speeds and to increase flow of cooling water through the engine 12 at wide open throttle speed. All non-varying discharge paths (i.e. tell-tale, or sprayer) for cooling water are located upstream of the cooling water jacket 54 on the catalyst housing 26, thus reducing condensation in the exhaust system 34 upstream of the catalyst 30.

With continued reference to FIGS. 21 and 22, the cooling water jacket 52 on the exhaust manifold 28 includes a series of cooling passages 110, 112, 114 including a first cooling passage 110 that conveys cooling water upwardly to the bend 66, a second cooling passage 112 that conveys the cooling water downwardly past the collecting passage 64, and a third cooling passage 114 that conveys cooling water back upwardly past the collecting passage 64 and exhaust manfold inlet runners 58 to the engine 12, namely the cylinder head 24 and cylinder block 20. The second cooling passage 112 has an inlet end 116 and an outlet end 118. The third cooling passage 114 has an inlet end 120 and an outlet end 122. An air purge passage 124 connects the inlet end 116 of the second cooling passage 112 and the outlet end 122 of the third cooling passage 114. In this manner, when the engine 12 is shut down, the air purge passage 124 allows air to flow from the outlet end 122 of the third cooling passage 114 to the inlet end 116 of the second cooling passage 112. When the engine 12 is started, the air purge passage 124 allows air to flow from the inlet end 116 of the second cooling passage 112 to the outlet end 122 of the third cooling passage 114. As discussed herein above, the type of air purge passage 124 can vary and as discussed herein above can include at least one of a jumper hose, a cross-drilled hole, a cast hole, and a cast-in-metal tube. Preferably, the air purge passage 124 is located vertically above the plurality of exhaust manifold inlet runners 58, the collecting passage 64 and the bend 66.

With continued reference to the embodiment shown in FIG. 22, the series of cooling passages 62, 63 in the cylinder head 24 includes a first cooling passage 62 and a second cooling passage 63. The first cooling passage 62 conveys the cooling water downwardly in the cylinder head 24 and the second cooling passage 63 conveys the cooling water upwardly in the cylinder head 24. The first cooling passage 62 includes an inlet end 126 and an outlet end 127. The second cooling passage 63 includes an inlet end 130 and an outlet end 132. An air purge passage 134 connects the inlet end 126 of the first cooling passage 62 to the outlet end 132 of the second cooling passage 63. In this example, when the engine 12 is shut down, the air purge passage 134 allows air to flow from the inlet end 126 of the first cooling passage 62 to the outlet end 132 of the second cooling passage 63, thus more efficiently purging air from the system. The air purge passage 134 can optionally include a milled hole, a drilled hole and/or a gasket.

Referring now to FIG. 10, the bend 66 has a curved radially outer wall 202 that has an upstream end that merges with an uppermost radially inner wall 206 of an uppermost inlet runner 208. The uppermost radially inner wall 206 of the inlet runner 208 horizontally extends and merges with the upstream end of the radially outer wall 202. The uppermost radially inner wall 206 extends to an uppermost location 210 on the curved radially outer wall 202 so that the exhaust gases conveyed through the uppermost inlet runner 208 flow horizontally through the collecting passage 64 and then downwardly in the bend 66, as guided by the radially outer wall 202. In other words, the uppermost radially inner wall 206 is horizontally aligned with the uppermost location 210 on the curved radially outer wall 202. This advantageously minimizes the length of exhaust routing prior to entering the catalyst 30. As shown in FIG. 10, the exhaust manifold 208 does not vertically extend above the cylinder head 24 and cylinder block 20. The present inventors have found that the exhaust gases that flow through the uppermost exhaust manifold inlet runner 208 advantageously tend to straighten exhaust gases that flow in a swirling flow from the remaining exhaust manifold inlet runners 58 located below the uppermost exhaust manifold inlet runner 208. Having the top of the bend 66 at the same height or a lesser height as the uppermost runner 208 minimizes overall engine height and weight.

Referring to FIG. 10, the bend 66 has an outlet end 212 that has an outlet centerline C2 that is horizontally offset from the catalyst centerline C1. The outlet centerline C2 is located closer to the collecting passage 64 than the catalyst centerline C1. The exhaust gases tend to follow the curved radially outer wall 202 of the bend 66 and thus are directed along the catalyst centerline C1, so that the exhaust gases advantageously are evenly distributed across the upstream end 220 of the catalyst 30. This also provides for improved packaging of other components. For instance, the space that is gained can be used to package an alternator.

Referring to FIG. 8, the gas concentration sensor 36 is located upstream of the catalyst 30 and downstream of the bend 66, at a location that is adjacent the curved radially outer wall 202. The sensor 36 is located upstream of a divergent section 214 of the exhaust manifold 28, located upstream of the catalyst housing 26. The sensor 36 has a tip 216 that is angled downwardly so that any condensation in the sensor 36 drains from the tip 216. The second gas concentration sensor 37 is located downstream of the catalyst 30 and upstream of a convergent section 218 of exhaust conduit. The sensor 37 has a tip 221 that is angled downwardly so that any condensation drains from the tip 221. The sensors 36, 37 are located so as to equally sense characteristics of the exhaust gases from all cylinders. The sensor 36 is located outside of the bend 66 because exhaust gases tend to follow the outside of the bend 66. The sensor 36 is also placed upstream of the divergent section 214 of the exhaust manifold 28 because the exhaust gases naturally slow down and diffuse in the divergent section, which may prevent the sensor 36 from equally sensing exhaust gases from all cylinders. The sensor 37 is placed as near as practical to the outlet of the catalyst 30 to avoid potential for water contact. The sensor 37 is placed upstream of the convergent section 218. The inventors have also found it desirable to mount the sensors 36, 37 with their respective tips 216, 221 angled downwardly so as to allow for any possible water/condensate to drain out of the respective sensor and not contact the sensing element. The sensor 37 is located towards the back of the engine 12, i.e. toward the cylinder head. The front and rear sides of the convergent section 218 are essentially vertical. By slightly tilting the mounting boss for the sensor 37 on the front or rear side of the convergent section 218, the sensor 37 can be positioned with its tip 221 pointed downwardly. Placing the sensor 36 outside of the bend 66, oriented toward the front of the engine 12 (towards the crank case portion of the cylinder block 20) allows the sensor 36 to be placed in a location that permits the tip 216 to drain. This also keeps the sensor 36 close to the cylinder block 20 so that the sensor 36 and related wires do not interfere with the cowl. This can be especially important with respect to the sensor 36 to avoid damage during installation/removal of the cowl.

Referring to FIG. 4, the catalyst 30 is disposed in the catalyst housing 26 such that exhaust gases flow into an upstream end 220 of the catalyst 30 and out of a downstream end 222 of the catalyst 30. A flange 224 is located on the upstream end 220. The flange 224 is sandwiched between the connecting surfaces 44, 46 of the exhaust manifold 28 and catalyst housing 26 to retain the catalyst 30 in place. The gasket 42 can be disposed between the flange 224 and the surface 44 of the exhaust manifold 28, as discussed herein above.

In this example, the catalyst 30 completely resides in the catalyst housing 26. The catalyst 30 is sized with respect to the catalyst housing 26 so that an air gap exists between the catalyst 30 and the catalyst housing 26. The flange 224 can be configured to prevent exhaust gases from bypassing the catalyst 30 via the noted air gap. The gasket 42 can include a sealing bead disposed around the peripheral surface 94 for sealing with the connecting surface 44 of the exhaust manifold 28. The present inventors have found that this design reduces issues associated with thermal growth of the overall exhaust system due to the additional thermal load of the catalyst 30. The lower end of the catalyst housing 26 is free to move axially and laterally as the catalyst housing 26 deforms due to temperature changes. The bottom of the lower exhaust pipe 32 can also be free so there is no additional stress placed on the drive shaft housing 16, adapter plate 14 or other structural components due to thermal growth. Placement of the flange 224 on the inlet end 220 of the catalyst 30 prevents exhaust gases from flowing around the periphery of the catalyst 30 and getting trapped by the catalyst housing 26. This aspect, combined with the fact that the catalyst 30 is inserted from the top of the catalyst housing 26, allows condensation to drain round the periphery of the mantle of the catalyst 30. The surface 46 of the catalyst housing 26 has a recess 225 that forms a shoulder to fit the catalyst flange 224 as the catalyst 30 is inserted into the catalyst housing 26. The gasket 42 is installed on top of the catalyst housing 26 and catalyst 30. The exhaust manifold surface 44 is flat at the mating flange and retains the catalyst 30 by applying pressure through the gasket 42 to the catalyst flange 224. For a rubber coated metal gasket a sealing bead can be added to the gasket 42 to ensure pressure is applied around the entire circumference of the catalyst flange 224. The sealing bead is an optional feature. The air gap between the catalyst 30 and catalyst housing 26 allows for different radial thermal growth amounts since the catalyst 30 will operate at a much higher temperature that the housing 26. This also reduces the heat transfer between the components to maintain adequate operating temperature of the catalyst 30.

In the present description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes only and are intended to be broadly construed. The different apparatuses described herein may be used alone or in combination with other apparatuses. Various equivalents, alternatives, and modifications are possible within the scope of the appended claims. 

What is claimed is:
 1. An outboard marine propulsion device comprising: an internal combustion engine having a cylinder head and a cylinder block; and an exhaust manifold that discharges exhaust gases from the internal combustion engine towards a vertically extending catalyst housing; wherein the exhaust manifold has a plurality of horizontally extending inlet runners that receive the exhaust gases from the internal combustion engine, and a vertically extending collecting passage that conveys the exhaust gases from the plurality of horizontally extending inlet runners to a bend that redirects the exhaust gases downwardly towards the catalyst housing; wherein the bend comprises a curved radially outer wall; and wherein an uppermost inlet runner in the plurality of horizontally extending inlet runners has an uppermost radially inner wall that horizontally extends from an uppermost cylinder in the cylinder head to an uppermost location on the curved radially outer wall so that the exhaust gases flow only horizontally through the collecting passage and then downwardly in the bend; wherein the uppermost radially inner wall is horizontally aligned with the uppermost location on the curved radially outer wall such that exhaust gases that flow horizontally through the uppermost inlet runner tend to straighten exhaust gases that flow in a swirling flow from the remaining inlet runners in the plurality of inlet runners.
 2. The device according to claim 1, wherein the exhaust manifold does not vertically extend above the cylinder head and cylinder block. 